Electric cut-out



Patented 'May 9, 1939- PATENT ori-lcs ELECTRIC CUT-OUT Ralph R. Pittman and Carroll H. Walsh,

, Pine Blull', Ark.

Application August z5, 1931, serial No. 160,864

7 claims.

This invention relates generally to high tension cutouts, and particularly to a unitary enclosed lightning arrester and expulsion fuse device for use on high tension electric distribution circuits.

This invention is an improvement upon the construction shown in United States Patent 2,034,204, dated March 17, 1936, issued to Ralph R. Pittman.

Among the objects of the present invention are; (l) the provision in a compact assembly, including a lightning arrester and a fuse, of insulated means for removing the assembly from its housing for inspection and/or repair; (2) the provision of enclosed and isolated line, load, and

' ground terminals for the prevention of accidental contact therewith; (3) vent means for directing the gaseous discharge attending the operation of either the lightning arrester or the fuse, or both, in a downward direction, together with resilient contact means for absorbing upward movement due to recoil from such discharge; (4) the provision of a novel lower contact and fuse terminal arrangement, which, in responsive to the blowing of a fuse link within the fuse tube, simultaneously pulls the unburned portion of the link out of the lower end of the fuse tube, disconnects the fuse tube from the load terminal, and visually indicates that the fuse has blown.

The invention comprises the elements and combinations thereof, and features of construction which will be exemplied in the structures hereinafter described, and the scope of the application of which will be set forth in the appended claims. y

One of the embodiments of the invention is illustrated in the accompanying drawing, in which Fig. 1 is a vertical sectional view of the device, showing the elements in the normal position with the fuse link intact.

Fig. 2 is a sectional View of the device, taken along the line II-II of Fig. 3.

Fig. 3 is an end view of the device.

Fig. 4 is another section view of the device, taken along the line IV-IV of Fig. 2.

Similar reference numerals indicate corresponding parts throughout the several views of the drawing.

Referring rst in particular to Fig. 2, a housing or fuse box Illiopen at its lower end, carries at the lower eng'lthe hook 53 for receiving the pin 54 of thei door 25, the latter carrying the eye 26 for convenience in moving the door to open and closed positions. In the open position the door is entirely detachable from the box, by lifting the pin 54 from the hook 53, but not detachable in the closed position. Both the door and the box are composed of some suitable insulating material, such as porcelain or Bakelite.

'Ihe lightning arrester-expulsion fuse unit has a numberof elements in common with the unit (Cl. 20G-115) shown in the above mentioned patent, among which are the expulsion fuse tube I'l, the upper fuse contact I3, the fuse link terminal plug 30, the fuse link I8 together with its fusible element 3I, the fuse link I8 extending through the bore of the fuse tube, the nested tubes of gas evolving yinsulating material 32 and I4, the gas expansion chamber I5 having the hollow 50, the internally threaded downwardly extending sleeve 5I for cooperating with similar threads on the fuse tube I1, and the upper and lower spaced conducting electrodes 33 and 34, the latter being arranged to provide a path of lowest electrical strength, or the preferential electrical path, from the upper fuse contact I3 to the conducting gas chamber I5. The arrangement and function of these particular elements is substantially the same as that of the corresponding elements shown in the above identified patent.

c Since the gases attending the occurrence of an arc between the electrodes 33 and 34 are highly conducting, it is essential that they be conducted to a point from which they may discharge outside of the box. For this reason, the gas charnber I5 is provided with a downwardly extending portion 52 having internal threads, and a hollow tube of insulating material I6, having threads cooperating with those of the portion 52, extends downwardly longitudinally along the fuse tube I1 to a point near the bottom of the box, thus providing a discharge conduit for the gases attending the operation of the arrester. As a further precaution against difficulty from conducting gases, the partition 38 of the box, and the partition 39 of the door overlap one another, to prevent conducting gases from bridging live parts of the device.

The lightning arrester-expulsion fuse unit just described is rigidly secured to the door 25 at its upper end by the encircling support 2S, and at its lower end by the screw 43, the latter rigidly fastening the lower support 24 to the door. The support 24 is conveniently provided with a pair of vertical openings through which the discharge conduit I6 and the fuse tube Il are pressed.-

The fuse tube I1 and the tubular insulators I4 and 32 are preferably of hard fiber because of its desirable combination of strength and arcextinguishing quality. 'Ihe arc-extinguishing quality is due to large extent to the moisture content of the ilber, the presence of which makes this material susceptible to damage from creepage or leakage currents unless the circuit containing these elements is open, or unless the material is short-circuited, as is normally the case with the fuse tube.

Internally of the box I0, and adjacent to the upper end thereof, is secured the line terminal II, into which the line conductor 55 extends, these members being held in electrical contact -zontally toward the gas chamber I5 in spaced relationship therewith, the elements 23 and I5 thereby constituting the spark gap 56, the purpose of which is to prevent the passage of leakage or creepage current from the line conductor 55 to the ground conductor 31 through the tubular insulator I4.

Within the lower portion of the box I is secured the load terminal 22, into which the load conductor 42 extends, the load terminal screw 4I maintaining these members in electrical connection. The load terminal contact mounting screw 40 secures the resilient load terminal contact 2| to the top of the load terminal 22, the load terminal contact 2| extending downwardly and inwardly toward the back of the box III.

At the lower open end of the box I0, the support 24 is provided with an inwardly extending ear 44, and the conducting lower fuse terminal member, or load terminal contact-engaging member I9 is pivotally mounted thereon for rotative or swingable movement about the pivot 45. 'Ihe contact engaging member I9 includes the upwardly extending portion 46, and the outwardly extending portion 41, the upper end of the portion 46 being arranged to engage the resilient load contact 2I when the portion 41 is substantially in a horizontal position, and the door 25 is closed. 'I'he fuse terminal stud 48, together with the knurled nut 49, provide means for securing the lower end of the fuse link to mechanically and electrically connect it to the contact engaging member I9. A semaphore 29, which may be simply an enlarged portion of the member I9, is provided at the end of the outwardlyextending portion 41.

The operation of the device is as follows:

Assuming the door 25 opened and removed from the box III, the fuse link terminal plug 38 is removed, and the fuse link I8 passed downwardly through the fuse tube I1. 'I'he plug 30 is then replaced, this maintaining the upper end of the fuse link I8 in electrical connection with the upper fuse contact I3, and mechanically fastened thereto. 'I'he load terminal contact-engaging member I 9 is then swung about the pivot 45 until the portion 41 is in a horizontal position, and the other or lower end of the fuse link I8 secured under the knurled fuse terminal nut 49.

'I'he door is nowreplaced on the box, and closed. Under this condition, the upper fuse contact I3 frictionally engages the resilient line terminal contact I2, and the contact-engaging member I9 engages the resilient load terminal contact 2l thus completing through the fuse link I8 and the contact-engaging member I9 an electrical circuit from the line conductor 55 to the load conductor 42. It will be observed that the upper end of the contact-engaging member I9 is now being urged outwardly by the resilient load contact 2l, and this force is in a direction to rotate the contactengaging member I9 to a position of disengagement with the load contact 2i. Such motion is prevented by tension in the fuse link I8, the latter being'attached to the member I8 at such a point with respect to the pivot 45 and the point of engagement of the contact 2| with the contact-engaging member I9 that a small amount of tension in the fuse link will resist a relatively large engagement pressure, in order to avoid mechanical rupture of the fuse link.

With the device in the service position just described, assume that an overvoltage, such as might be caused by lightning, is impressed on the line conductor 55. Since the construction is such that the weakest electrical path from the line conductor 55 to the ground conductor 31 includes the internal gap between the electrodes 33 and 34, and air gap between the member I5 and the electrode 23, it is over this path that the excess voltage will be discharged to ground. Following the breakdown of the gap between the electrodes 33 and 34, any arc following the sparkover will be extinguished by its connement between the tubular insulators of gas evolving material I4 and 32, and the gaseous products discharged from the hollow 58 of the gas chamber I5 through the conduit I6 to the atmosphere. The device requires no attention following this operation.

y Still with the device in the service position illustrated by Fig. 1, assume that an overcurrent, such as might be caused by either a short-circuit or an overload, passes from the line conductor 55 to the load conductor 42. The thermal eiect of such current fuses the fusible element 3l of the fuse link I8. Upon the rupture of the fuse link I8, the swingable contact-engaging member I9 is free to move about the pivot 45, and is urged in a clockwise direction by the bias of the resilient load terminal contact 2l, thereby causing the contact-engaging member I9 to reach the position illustrated in Fig. 2. It will be observed that the load terminal contact 2| is now electrically isolated from the fuse link I 8 and the fuse tube I1, and that the hanging portion of the fuse link Il is electrically disconnected from both the line and load terminals of the device. It may also be seen that the semaphore 20 has swung out of the lower open end of the box I0 from its previous concealed position within the box I0 to a visible position below it, thereby visually indieating that the fuse link has parted. Following this operation, it is necessary to re-fuse the device, as before described.

In view of the above, it will be apparent that advantageous results are attained by our invention, including the accomplishment of the several objects set forth. It may be mentioned that heretofore it has been common practice in the construction of electric distribution systems to employ individually mounted lightning arresters and cutouts. The reduction in cost, both of installation and construction, through the use of our invention, will be apparent to all familiar with the present state of this art.

While we have herein illustrated and described an embodiment of our invention, it will be obvious that changes could be made in the specic construction shown without departing from the scope of the invention. It is therefore intended that our drawing and description shall be interpreted as illustrative rather than limiting.

We claim:

1. A cutout comprising a housing of insulating material, spaced conducting line and load terminals within said housing, a door detachably moimted on said housing, an expulsion fuse tube rigidly secured to said door, said fuse tube spanning said terminals, a hollow tubular insulator of gas evolving material supported on said fuse tube between said terminals, spaced electrodes associated with said tubular insulator, said electrodes being arranged to provide a preferential spark path therebetween within said insulator, vent means for said insulator, said vent means including a gas collecting chamber at the lower end of said insulator and a hollow tube of insulating material in communication therewith extending longitudinally downward along said fuse tube, and means including a resilient line terminal contact mounted on said line terminal for absorbing the recoil due to the downward discharge of gas from either said expulsion fuse tube or said tubular insulator.

2. A cutout comprising a housingr of insulating material having an open lower end, spaced conducting line and load terminals within said housing, a door detachably mounted on said housing, an expulsion fuse tube rigidly secured to said door, said fuse tube spanning said terminals, a hollow tubular insulator of gas evolving material supported on said fuse tube between said terminals, spaced electrodes associated with said tubular insulator, said electrodes being arranged to provide a preferential spark path therebetween within said insulator, separate vent means for said insulator and said expulsion fuse tube, said vent means being arranged to discharge gas attending the operation of the device downwardly from the bottom of said housing, and resilient means for absorbing the upward endwise -movement due to the recoil attending gas discharge.

3. A cutout comprising a housing of insulating material having an open lower end, spaced conducting line and load terminals within said housing, a door detachably mounted on said housing, an expulsion fuse tube attached to said door, said fuse tube spanning said terminals, a hollow tubular insulator of gas evolving material supported on said fuse tube between said terminals, spaced electrodes associated with said tubular insulator, said electrodes being arranged to provide a preferential spark path therebetween Within said insulator, individual vent means for said insulator and said expulsion fuse tube, said vent means being arranged to discharge gas attending the operation ofthe device downwardly through the open lower end of said housing, resilient means for absorbing the upward endwise movement of said fuse tube and tubular insulator attending gas discharge, means including a tensioned fuse link within said fuse tube for electrically connecting said line and load terminals, and means responsive to the blowing of said fuse link for isolating the unfused portion of said fuse link from said load terminal.

4. In a protective device, insulating means, spaced conducting terminals mounted thereon, a fuse tube spanning said terminals, a fuse link extending through said fuse tube and electrically connecting said terminals, excess-voltage protective means associated with said fuse tube, said excess-voltage protective means including a hollow tubular insulator of gas evolving material supported on said fuse tube between said terminals and spaced conducting electrodes associated with said tubular insulator, said electrodes being arranged to provide a preferential spark path therebetween with said insulator,.and means including a conducting member pivoted at the lower end of said fuse tube and movable with respect thereto for electrically isolating said fuse tube, fuse link and said excess-voltage protective means from only said load terminal.

5. In a protective device,insulating means,spaced conducting terminals mounted theron, a fuse tube spanning said terminals, a fuse link extending through said fuse tube and electrically connecting said terminals, excess-voltage protective means associated with said fuse tube, said excessvoltage protective means including a hollow tubular insulator of gas evolving material supported on said fuse tube between said terminals and spaced electrodes associated with said tubular insulator, said electrodes being arranged to provide a preferential spark path therebetween within said insulator, a swingably movable member pivoted at the lower end of said fuse tube, means including a tensioned fuse link fastened to said movable member for maintaining the electrical connection of said line and load terminals, and means responsive to the' rupture of said fuse link for disconnecting said fuse link, fuse tube, and excess-voltage protective means from only said load terminal.

6. A cutout comprising a housing of insulating material having an open lower end, spaced conducting line and load terminals within said housing, a door mounted on said housing, an expulsion fuse tube secured to said door, said fuse tube spanning said terminals, a hollow tubular insulator of gas evolving material supported within said housing, spaced conducting electrodes associated with said tubular insulator, means electrically connecting one of-said electrodes to said line terminal, said electrodes being arranged to provide a preferential spark path therebetween within said insulator, and separate vent means for said insulator and said expulsion tube, said vent means being arranged Yto discharge gas attending the operation of the device downwardly from the bottom of said housing.

7. A cutout comprising* a housing of insulating material, spaced conducting line andload terminals within said housing, a door mounted on said housing, an expulsion fuse tube secured to said door, said fuse tube spanning said terminals, excess-voltage protective means associated with said fuse tube, said excess-voltage protective means including a hollow tubular insulator of gas evolving material supported within said housing, spaced conducting electrodes associated with said tubular insulator, means electrically connecting one ofsaid electrodes to said line terminal, said electrodes being arranged to provide a preferential spark path therebetween within said insulator, separate vent means for said insulator and said expulsion tube, said vent means being arranged to discharge gas attending the operation of the device to the outside of said housing, a movable fuse terminal member having an open and a closed position between said line and load terminals mounted at the lower end of said ruse tube, a tensioned fuse link which when unfused prevents movement of said fuse terminal member from the closed position, said fuse link normally electrically connecting said terminals, and means responsive to the rupture of said fuse link for 'actuating said fuse terminal member to the open position and electrically isolating said fuse tube, fuse link, and said excess-voltage protective means from only said load terminal.

RALPH R. PITI'MAN. CARROLL H. WALSH. 

